The construction of machine tables related to the invention disclosed herein are used mainly in change tables or pallets for use with processing centers or similar machines. The bearing surfaces of the machine tables or pallets and the support surfaces of the machine bed or frame are precision worked and in most cases additionally adjustable, so that the successively changed pallets assume at all times an exactly, reproducible position on the machine bed or frame. The bearing surfaces or rather support surfaces can moreover engage positively, so that they also absorb the forces which act onto the machine table in the table plane.
To prevent all forces from lifting the machine table off from the machine bed, the machine table is clamped onto the machine bed. One or several clamping devices are as a rule used for this, which members engage anywhere on the machine table and pull same toward the machine bed. However, a risk exists, primarily when between the bearing surfaces and the point of engagement of the clamping device or devices, there exist larger distances, that the machine table will bend or be distorted in the area of the clamping device and through this forms an inexact bearing surface for the workpiece fastened thereon.
A certain remedy can be achieved by distributing the entire tensioning or clamping force to as many as possible, each lightly loaded clamping devices so that in this manner the forces which act locally onto the machine table are kept small. From this results, however, primarily in the case of automatic clamping systems, a substantial amount of structural and technical control development and thus a very expensive mode of construction.
It is the purpose of the present invention to provide a device which permits with simple means a secure, deformation-free clamping of a machine table to a machine frame.
The inventive construction facilitates a clamping function with one single clamping device, even on larger machine tables. The centrally applied clamping force does not engage directly the actual table member, but is guided through the transmitting means substantially near the bearing surfaces, where they can be absorbed deformation-free by the support surfaces.
The transmitting means can be designed in any desired manner such that it distributes the centrally applied clamping force at an optimum to the bearing surfaces. A particularly simple and inventive design results if they are formed by a plate, which at least in the area of the bearing surfaces is connected to the underside of the machine table, while in their center area there is provided a device for the engagement of the clamping device.
A preferred embodiment provides that the plate is constructed as a circular disk, which is secured with its outer edge on the machine table and that it has an opening in its center, into which opening the clamping device, for example with an enlarged head which is automatically rotatable during the clamping or releasing movement, engages in a bayonetlike manner.
In a different exemplary embodiment, the circular disk is radially slotted, whereby the clamping device is provided with an enlarged head which extends over the lateral edges of the slot. In this solution, the machine table can be swung laterally into its operating position.
The plate or rather circular disk can be constructed basically in one piece with the machine table; however, it is constructed preferably as a separate structural part and is connected to the machine table through screws or similar fastening means.